Hepatocellular carcinoma (HCC) is the most common solid organ tumor and one of the most frequently encountered malignancies in the world. Likely a result of the hepatitis C epidemic of the 1970's and 1980's, the incidence of this cancer has doubled in the United States during the past decade and worldwide approximately 1 million new cases are diagnosed per year. Traditionally, curative therapy for early-stage HCC has been surgical. However, radiofrequency ablation (RFA) has recently gained popularity in the treatment of HCC. RFA offers a number of potential advantages over surgical therapy. It can be applied through a minimally invasive approach, may be performed as an outpatient procedure, allows treatment of HCC in care environments that do not have the resources to perform surgical resection or transplantation, and allows non-surgical practitioners (such as interventional radiologists) the opportunity to treat patients with HCC. RFA successfully ablates tissue, but its efficacy as a primary, curative treatment for HCC has not been well tested. How the community at large utilizes RFA is also unknown. Recent data suggests RFA is becoming a primary treatment option for early stage HCC without quality evidence to support this practice. The proposed research intends to use a large, population-based cancer registry (SEER) as well as linked Medicare claims data (SEER-Medicare) to better define how HCC is treated in the community at large, to detect trends in the use of RFA, and evaluate outcomes associated with HCC care. Using a cohort of patients diagnosed with HCC between 1992 and 2005, we plan to 1.) describe stage-specific temporal trends in RFA use;2.) characterize regional variation and patient- and physician/hospital-level factors associated with the use of RFA;3.) describe differences in 30-day mortality between patients who received RFA and those who underwent surgical therapy after adjusting for relevant factors;4.) describe differences in overall and cause-specific survival among patients with early-stage HCC who received RFA and those who underwent surgical therapy after adjusting for relevant factors. Logistic regression will be used to examine trends in RFA use over time and to evaluate potential predictors of RFA use. Logistic regression will also be used to explore the relationship between RFA use and early mortality while adjusting for stage as well as patient and provider factors. Cox multivariate regression will be used to explore the relationship between RFA use and long-term survival while adjusting for stage as well as patient and provider factors. This work has implications for improving the quality of surgical care and these findings will help to inform future, prospective clinical trials aimed at clarifying the role for RFA in the treatment of HCC